Recognize cooldown as an integer Bundler setting

Adds `cooldown` to NUMBER_KEYS so that `BUNDLE_COOLDOWN` and
`bundle config set cooldown` are parsed as integer days. Reading the
value is enough for now; later commits plumb it into the resolver and
the Gemfile DSL.

#9113

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: hsbt

bundler/lib/bundler/settings.rb

@@ -44,6 +44,7 @@ class Settings
     ].freeze
 
     NUMBER_KEYS = %w[
+      cooldown
       jobs
       redirect
       retry

spec/bundler/settings_spec.rb

@@ -119,6 +119,11 @@
         settings.set_local :ssl_verify_mode, "1"
         expect(settings[:ssl_verify_mode]).to be 1
       end
+
+      it "coerces cooldown to integer" do
+        settings.set_local :cooldown, "7"
+        expect(settings[:cooldown]).to be 7
+      end
     end
 
     context "when it's not possible to create the settings directory" do